<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="vue_dev.js"></script>
</head>

<body>
    <div id="app">
        {{date}}
    </div>
    <script>
    	var app=new Vue({
    		el:'#app',
    		data:{
    			date:new Date()
    		},
    		mounted:function () {
    			var _this=this;
    			this.timer=setInterval(function(){
    				_this.date=new Date();
    			},1000);
    		},
    		beforeDestory:function(){
    			if(this.timer){
    				clearInterval(this.timer);
    			}
    		}
    	})
    </script>
</body>

</html>